lib/oeqa/runtime: cleanup and improve output readability for some tests

lib/oeqa/runtime: cleanup and improve output readability for some tests

   - move everything in the same test. setUp/tearDown aren't quite
the right thing here, everything it's part of the same test. (and
it get's confusing when ssh fails)

ldd:
   - change test name and add output to error message

vnc:
   - remove unnecessary check as there is no point in doing
both ps and netstat. Also improve error output a bit.

(From OE-Core rev: 2f91bb438cfcdd0a40daed5902b6e98fc0aee67f)

Signed-off-by: Stefan Stanacar <stefanx.stanacar@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>